Variable level skimmer



April 7, 1953 E. M. KELLY ET AL 2,633,989

VARIABLE LEVEL SKIMMER Filed Nov. 5, 1949 2 SHEETS-SHEET 1 INVENTORJ: EARL M/(A-ZL Y ,4 7'TORA/EY.

FIG.

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April 7,1953 E. M. KELLY ET AL 2,633,989

VARIABLE LEVEL SKIMMER Filed Nov. 5, 1949 2 SHEETS-SHEET 2 INVENTORJ.

EARL M KELLY yuan I 5014mm,

Patented Apr. 7, 1953 VARIABLE LEVEL SKIMMER Earl M. Kelly, Millbrae, and Samuel I. Bousman,

Mountain View, Calif., assignors to Process Engineers Incorporated, San Francisco, Calif., a corporation of California Application November 3, 1949, Serial No. 125,226 8 Claims. (01. 210-51) This invention relates to skimming apparatus of the type used to remove floating material such as scum, foam, and solid particles from a body of liquid. Usually such skimming apparatus is used on a body of liquid passing through an elongated basin or tank, often referred to as a skimming pond.

Conventicnal'apparatus of this type generally consists of a trough and means, usually an elongated paddle, to urge the floating material up an inclined tray into the trough. The tray and trough form a so-called over-flow lip where they meet above the liquid level and over which the skimmed material is discharged into the trough. Means are provided for removing accumulated scum, etc., from the trough. As the material, whatever it may be, is carried up the inclined tray above the level of liquid in the tank, any free liquid has opportunity to drain back into the main body before the material is carried over the overflow lip. In this manner liquid loss into the trough is held to a minimum.

When the character and quantity of floating material is relatively uniform and the liquid level substantially constant, the skimming apparatus may be pre-set to give optimum performance. But once so set, it is not possible in present skimmers to achieve any variation in placement of the overflow lip, based upon changes in quantity or character of floating material, and even more important, on the level of the liquid body. There is a need for an apparatus which will adjust itself responsive to changes-in these operation variables. The circumstances giving rise to a need for such apparatus are frequently encountered in sewage treating plants where the volume of throughput varies over a considerable range at different times of year, and even during the course of a twenty-four hour period. In such installations, the design of the settling basins is often such that scum and other floating material accumulates on the surface. When the flow of liquid through these basins is uniform, it is a simple matter to remove the scum, etc., with conventional skimming apparatus. However, when the liquid level in such settling basins varies, such variation being frequently as much as several feet, the presently existing skimming apparatus is inoperative and remains so until the liquid returns to the level for which the apparatus is designed. v q

We have developed a skimmer, the position of which is adjustable to permit optimum operation even when comparatively large variations in liquid level are encountered. In accordance with our invention, we provide a skimmer for removing floating substances from a body of liquid comprising in combination a collecting trough, an inclined tray extending from a point beneath the level of liquid to the edge of a sidewall of the trough and terminating in an overflow lip, means for lifting the floating substances from the surface of the liquid up the inclined tray and discharging them over the overflow lip into the trough, and means for varying the elevation of the trough and inclined tray to maintain the overflow lip a predetermined distance above the liquid level.

In a preferred embodiment of the invention,

"' automatic means are provided operative responsive to changes in liquid level to adjust the position of the trough, etc., to maintain a fixed preselected distance between the surface of the liquid and the overflow lip. In this preferred embodiment, the apparatus may operate continuously even while the liquid level is in the process of changing and hence, is notdependent upon steady conditions.

The invention will be more clearly understood from the following detailed description thereof taken in conjunction with the accompanying drawing in which:

Fig. 1 is a sectional elevation through a conventional skimming pond or settling basin with one form of the apparatus of the invention mounted therein; I

Fig. 2 is a plan viewofthe skimming apparatus of Fig. 1;

Fig. 3 is a horizontal section taken on the line 3-3 of Fig. 1;

Fig. 4 is a sectional elevation taken on the line 4-4 ofFig.1;

Fig. 5 is an enlarged sectional elevation taken on the line 5-5 of Fig. 4; and p Fig. 6 is a partial sectional elevation showing an alternative embodiment of the apparatusof Fig.1.

In the drawing, the apparatus of the invention is shown installed in a concrete basin or channel H3 having sidewalls EBA, MB and a bottom IflC inclined from wall to wall. A stationary rec'- tangular supporting framework [2 is rigidly mounted across the basin, being supported above the sidewalls by legs I2A, 12B, I20 "and I2D. Guides l3, l4 depend from the framework 12 ad jacent one wall I013 and a like pair of guides 55, I5 depend from the framework adjacent the other wall [9A. The several guides I 3, [4, etc., extend vertically downwardly from the supporting framework l2 beneath the surface of liquid I! in the channel.

A second or travelling framework 18 is suspended from the stationary framework in vertically adjustable relationship by lift screws 32, 33 affixed to hangers 33, 3|, respectively. The lift screws are suspended from the stationary framework in vertically slideable relationship. The travelling framework is provided with a plurality of rollers 39, 49, ll, 42, etc., there being a total of eight such rollers placed at the eight corners of the framework and engaging in the guides l3, l4, l5, IS. The travelling framework may be raised or lowered with respect to the'stationary framework by the lift screws. A trough 2!! is fastened to the framework l 8 extending substantially from side to side of the channel. The trough has a funnel-shaped bottom opening into a discharge line 22 (see Fig. 1). An inclined feeder tray 26 is fastened to the travelling framework and extends from end to end of the trough. One edge of the tray (which may be formed integrally with the trough) forms an overflow lip 25 with an edge of the trough (Fig. 4). The tray slopes outwardly and downwardly from the trough so that. its opposite longitudinal edge 25 lies below the surface of the liquid in the basin (Fig. 4).

A skimmer structure 28 is rotatabl mounted between end supports forming a part of the travelling framework and includes two elongated blades 28A, 28B, the outer edges of which slide along the tray 24 when the scraper is rotated to liftscum or. other floating material from the surface of the liquid over the overflow lip 25 into the trough. 20. The skimmer is rotatably journaled ateither end in pillow blocks 48, 59 supported at the ends of the travelling framework. The arrangement is shown in detail in the enlarged sectional elevation of Fig. 5, wherein the pillow block 49 is fastened to the end member of the framework I8. A spindle 56 is journaled through a roller bearing and a sealing gasket 52 in the pillow block. A bushing 53 is mounted on the inner end of a spindle 5G and a tubular hub 38 of w the scraper 28 is mounted over the bushing 53. A sprocket 56 is afiixed on the outer end of spindle 58 and is connected by a chain 5'! to a sprocket 58 mounted on the drive shaft. of motor 60. The motor Silis mounted on th travelling framework so that operation of the skimmer is independent of the position of the travellin framework and may be carried on even though the travelling framework is in the process of adjustment.

The discharge pipe 22 of the scum trough 2i? extends into a standpipe A l connected to a drain pipe 45. The discharge pipe 22 is slide-able in the standpipe through a packing gland 45, the depth of insertion of the pipe 22 in the standpipe being dependent upon the vertical position of the scum trough 2!) (Figs. 1 and 4).

Preferably, the adjustment of the scum trough is made automatically responsive to the level of liquid in the basin so as to eliminate the error inevitably attendant upon manual control and to reduce the cost of operation. One means of automatic adjustment is shown in Figs. 1 and 2. A reversible motor 64 is mounted on the stationary framework and its drive shaft is connected by a conventional belt and pulley or chain and sprocket arrangement 54A to an elongated shaft 85. The shaft 65 is connected at its opposite ends through suitable gear means. as for example, the worm and worm gear combinations 66, 6? and 66A, 51A to raise'or'lower the lift screws 32, 33.

One means of accomplishing this is shown in the drawing. The screws 32, 33 are threaded through the Worm gears 61, 67A which are rotatably mounted in brackets 34, 35. Rotation of the Worm gears responsive to rotation of the shaft thus causes the lift screws to travel in one direction or the other with respect to the longitudinal axis of the gear. The threads on the two lift screws and associated worm gears are arranged so that rotation of shaft will result in displacement of both lift screws in the sam direction and by the same amount.

A stilling well I8 is provided adjacent a side o the channel I8 and is connected to the main body of liquid in the channel through a port 12 in the side of the channel. The liquid in the stilling well 76 will be at the same level as the liquid i the tank Ill but will be free of turbulence because of its relative isolation from the main body of liquid.

The operation of the motor 64 may be controlled responsive to the liquid level in the stilling well Ill in a number of ways. One such control means is shown in Figs. 1 and 2 and comprises a commercially available level controller 14 which is, in effect, a variable capacitor, the capacity of which varies as a function of the depth of immersion of the controller. As the liquid level in the stilling well Varies, the capacity of the controller 14 varies proportionately and this variation in capacity is used to operate a relay or other electronic switch means (not shown) located in a control box 76 and connectedto control the motor as. The level controller M is mounted to travel with the travelling framework, for example, on the bracket arrangement 78. The arrangement is such that any desired position of the overflow lip with respect to the surface of the liquid in th basin may be maintained. The apparatus is Se so that the capacity of the level controller at this pro-selected position renders the motor 64 inoperative. If the capacity of the, level controller either increases or decreases from the preselected or steady-state capacity responsive to rise or fall of liquid level, the motor 64 will be energized to rotate the shaft 65 in the M 1 direction to raise or lower the travelling framework 38. The motor will continue to run until the system attains a position at which the steadystate capacity of the level control is again achieved.

In'the particular embodiment shown in Fig. 1, the level control 14 is enclosed ina tubular jacket 80 extending into the stilling well it, further protecting the level controller from minor fluctuations of liquid level which might result from wind or other factors tending to produce lilllbll" lence in the main body of liquid. A pipe manlfold 82 is connected to the well 80 so that scum or other undesired accumulations may be flushed periodically out of the well.

The maximum travel of the'scum trough, up or down, is established in the original desi n and limit switches 83 (Fig. 1) are provided to keep the movement within the design limits. The limit switches are connected to render the motor 64 inoperative so long as either is closed.

An alternative automatic control mechanism is shown in Fig. 6, which is a sectional elevation through the stilling well 10. This mechanism comprises a group of four electrodes 86, B7, B8, 89. arranged in pairs to control the raising or lowering of the travellin framework through operation of the motor 64. The electrodes 86, 81, when a circuit is closed therebetween operate the motor to raise the'travelllng framework. To accomplish this, the electrode 36 terminates just above the liquid and the electrode 8'! terminates I in contact with the liquid. Any rise in the liquid level to contact electrode 86 closes a circuit between the electrodes 86, 81, energizing the motor 64 to raise the travelling framework and the electrode assembly to the point where th electrodes 86, 81 assume the same relative position to the liquid level as shown in the drawing. The electrode pair 88, 89 is arranged with the electrode 88 just contacting the surface of the liquid and the electrode 81 extending a short distance into the liquid. Any lowering of the liquid level breaks the circuit between these electrodes which circuit break is used to energize the motor 64 in the opposite direction to lower the travelling framework 38 and the electrode assembly to return electrodes 88, 89 to the relative position with respect to the new liquid level. I

The automatic control system shown in Figs. 1 and 2 is preferred over that shown in Fig. 6 because of the simplicity, and it is not limited to use with conductive liquids as is the arrangement shown in Fig. 6. e l r l Float switches or other liquid level responsive means may be used to initiate, through a suitable circuit, the operation of motor 64. The motor 64 maybe operated automatically responsive to changes in liquid level as described, or may be operated from manually controlled switches. Automatic control is preferred because more sensitive and rapid response is obtained and the apparatus requiresless attention. In either case,

the motor 60,- which drives the skimmer or 1 scraper, is completely-independent in its operation and if energized continuously, will continue to cause scum, etc., to be discharged into the trough 20 even while the trough and feeder tray are being raised orlowered to compensate for changes in liquid level.

In many instances, accumulation of scum, etc., is at such a rate that it is not necessary to operate the skimmer continuously. In one commercial installation, the operator has found that operation of the skimmer for a few minutes out of every hour or'two is suflicient to remove the scum. However, between times, the trough, feeder tray, and skimmer move up and down as a single unit responsive to changes in liquid level 5 and act as a scum dam. When scum accumulation again warrants operation of the skimmer, it will be in the correct position. Under these circumstances, a single operator will sufiice for a number of installations since his only concern c is with starting the scraper motor 80 when an accumulation offloating material develops.

To summarize, the trough is raised and lowered with the liquid level. It carries a sloping tray and a rotating skimmer which dips into the liquid level and pushes scum and other floating material up the sloping tray above the liquid level and over a lip into the trough. As the scum is pushed up the inclined tray, it has an opportunity to drain. The drained scum which is carried into the trough drains out through the standpipe connected with the bottom of the trough.

The trough-tray-skimmer assembly may be employed as a dam to collect scum in a channel until there is sufficient to warrant the rotation of the skimmer, which is driven by a motor mounted on the assembly.

The raising and lowering of the trough may be manual, for example, by substituting a hand wheel for the motor 64. Thus the lift screws may be turned simultaneously in one direction to bring about raising or lowering of the trough. However, it is preferable to drive the lift screws. with the motor and to control it automatically by means responsive to changes in the liquid level.

We claim:

1. Apparatus for removing floating materials from a body of liquid in a basin comprising a first framework stationarily mounted across and above the basin, a second framework suspended from and vertically adjustable with respect to the first framework, a trough affixed to the second framework for collection of said floating m terials, an inclined tray extending from an edge of the trough downwardly and outwardly therefrom, an elongated paddle rotatably mounted on said second framework and positioned to engage against the upper surface of said tray during rotation, means mounted on said second framework for rotating the paddle, and means inclucling a prime mover for raising and lowering the second framework with respect to the first framework.

21 Apparatus for removing floating materials from a body of liquid in a basin comprising a first framework stationarily mounted across and above the basin, a second framework suspended from and vertically adjustable with respect to the first framework, a'trough affixed to the second framework for collection of said floating mate' rials, an inclined tray extending from an edge of the trough downwardly and outwardly therefrom, an elongated paddle rotatably mounted on said second framework and positioned to engageagainst the upper surface of said tray during rotation, means mounted on said second framework for rotating the paddle, and means including a prime mover for raising and lowering the second framework with respect to the first framework to maintain the upper edge ofthe tray a fixed distance above the surface of said body of liquid.

3. Apparatus for removing floating materials from a body of liquid in a basin comprising a first framework stationarily mounted across and above the basin, a second framework suspended from and vertically adjustable with respect to the first framework, a trough afllxed to the second framework for collection of said floating materials, an inclined tray extending from an edge of the trough downwardly and outwardly therefrom, an elongated paddle rotatably mounted to said second framework and positioned to engage against the upper surface of said tray during rotation, a motor mounted to said second framework for rotating the paddle, means including a prime mover for raising and lowering the second framework with respect to the first framework and means including a liquid level follower for controlling said prime mover responsiveto variations in liquid level to maintain the upper edge of the tray a fixed distance above the surface of said body of liquid.

4. Apparatus for removing floating materials from a body of liquid in a basin comprising a first framework stationarily mounted across and above the basin, a second framework suspended from the first framework by lift screws and vertically adjustable with respect to the first framework, atrough affixed to the second framework and opening into a vertically adjustable discharge manifold, an inclined tray extending from an edge of the trough downwardly and outwardly therefrom and forming an overflow lip with the trough, an elongated paddle rotatably mountedto said second framework and positioned to engage against theupper surface ofxsaid tray during rotation to scrape floating materials up the tray into the trough, means mounted to said second framework for rotating the paddle, and means including a prime mover and a liquid level follower for raising and lowering the second framework with respect to the first framework to maintain the overflow lip a fixed distance above the surface of said body of liquid.

5. Apparatus according to claim 4, wherein the prime mover comprises a reversible motor, and means connecting the motor to said lift screws so that rotation of the motor shaft is translated into simultaneous raising or lowering of said lift screws.

6. Apparatus for removing floating materials froma body of liquid in a basin comprising a first framework stationarily mounted across and above the basin, a second framework suspended from the first framework by lift screws and vertically adjustable with respect to the first framework, a trough affixed to the second framework, a drain pipe in the bottom of the basin, a discharge pipe opening into said trough and into said drain pipe, the discharge pipe being affixed to the trough and vertically slideable in the drain pipe, an inclined tray extending from an edge of the trough downwardly and outwardly therefrom and forming an overflow lip with the trough, an elongated paddle rotatably mounted to said second framework and positioned to engage against the upper surface of said tray during rotation, means mounted to said second framework for rotating the paddle, a reversible motor mounted on said first framework and mechanically connected to raise and lower said lift screws in unison, and control means including a liquid .level follower for controlling said motor responsive to variations in the level of liquid in the basin to maintain the overflow lip a fixed distance above the surface of the liquid.

7. Apparatus according to claim 6, wherein said liquid level follower comprises a. stilling well adjacent the basin and connected to the basin below the surface of the liquid in the basin, and electrical means disposed in contact with the liquid in the stilling well for actuating said motor responsive to variation in liquid level in the stilling well.

8. Apparatus according to claim 7, wherein said electrical means is mounted to said second framework to move vertically in the stilling well responsive to vertical motion of said second framework.

EARL M. KELLY. SAMUELI. BOUSMAN.

REFERENCES CITED The following references are of record in the Number Name Date 1,450,545 Hans Apr. 3, 1923 1,582,715 Wensley Apr. 27, 1926 1,625,592 Conant et al. Apr. 19, 1927 1,843,329 Lathrop Feb. 2, 1932 1,860,819 Schamberger May 31, 1932 2,086,730 Miickv July 13, 1937 2,102,575 Shafer, Jr. Dec. 14, 1937 2,140,059 Simonsen Dec. 13, 1938 2,226,974 Hardinge Dec. 31, 1940 2,237,172 Briggs Apr. 1, 1941 2,349,972 Lister May 30, 1944 2,455,338 Lind Nov. 30, 1948 FOREIGN PATENTS Number Country Date 536,259 Germany Oct. 21, 1931 

